The Denver police gang unit has taken over the investigation of a shooting that injured two people in the legs and grazed one other bystander at a massive pot rally celebrating Colorado's legalization of marijuana.

Investigators spent the night scanning videos taken at Saturday's 4/20 rally and are asking anyone who witnessed the shootings that injured three at Civic Center to come forward.

The police gang unit is taking the lead on the investigation athough it is not yet clear if gangs were involved, police spokesman Sonny Jackson said. "They have their ears to the ground and take care of this sort of thing," Jackson said.

The shooting broke out at about 5 p.m. at the annual celebration of marijuana, and sent attendees scrambling to escape.

Denver police said two people who were shot in their legs were rushed to a hospital with non-life-threatening injuries. A juvenile was also grazed by a bullet walked to a nearby hospital.

"When gunfire happens people run away. Now that things have calmed down, we would like them to come back and talk to us," police spokesman Sonny Jackson said on Sunday.

Officers are searching for two suspects.

Andrew Lindsley, who was nearby when the shots rang out, said that when he saw two men "coming aggressively through the crowd," he thought trouble was on the way.

He continued walking past the two and a few seconds later he heard gunshots and started running, he said. "It was absolutely gang-related," he said.

Saturday's rally -- an annual event called 4/20 that is a holiday for marijuana enthusiasts -- was the first since Colorado voters legalized use of marijuana for people over 21.